1. Field of the Invention
This invention relates to computer systems and, more particularly, to backup and restoration of data within computer systems.
2. Description of the Related Art
There is an increasing need for organizations to protect data that resides on a variety of client devices via some type of backup mechanism. For example, numerous client devices may be coupled to a network to which one or more media servers are also coupled. The media servers may include or be further coupled to a storage unit consisting of one or more disk storage devices, tape drives, or other backup media. Media servers and backup media may provide low-cost, long-term archival storage of data. A backup agent on each client device may convey data files to the media server for storage according to a variety of schedules, policies, etc. For example, large backup datasets may be moved from a client device to a media server configured to store data for later retrieval, thereby protecting data from loss due to user error, system failure, outages, and disasters, etc. as well as archiving information for regulatory compliance, workflow tracking, etc.
Unfortunately, data stored on archival backup media may not be readily available to the client devices. For example, restoration of data may require an administrator to locate and mount a tape, drive, or other device, before the data may be accessed. Consequently, client devices may backup and restore data in a disk-based backup store via one or more host devices coupled to the network in addition to archival storage on backup media. In some cases, single-instance storage techniques may be used in which datasets are segmented and the segments are de-duplicated to reduce the required disk capacity. Conventional archival techniques and single-instance techniques may be mixed in the same backup environment.
In order to make data more readily available, one or more metadata managers may store metadata in a catalog, the metadata describing the associated data in the backup store. Such a catalog may be referred to as a metabase. Metadata managers may be located on separate hosts or co-located on hosts that include a backup store. Accordingly, one or more metabases hosted in a variety of locations may contain data describing a backup store.
To facilitate finding data entities that are stored in a backup store, file system user interfaces may be provided on client devices. For example, files in a backup store may be read through interfaces that provide some of the capabilities of Network File System (NFS) or Common Internet File System (CIFS). Unfortunately, these interfaces do not provide the ability to write to, modify, or create multiple versions of files in a backup store. It may be desirable to perform a variety of operations on data that is stored in a backup store. For example, after a backup, it may be desirable to verify the correctness and usability of files in a backup store. Unfortunately, without write access to the backup store, finding and correcting errors requires the files to be restored first, a costly and time-consuming operation.
In addition to the above considerations, it is sometimes desirable to move backup data from a disk-based backup store to an archival backup medium. For example, data may be stored in a backup store on a frequent basis using single-instance techniques so that it is readily available to recover from inadvertent deletion. The same data may be moved to a backup archive for regulatory compliance on a less frequent basis. While it is possible to create an archival backup copy of a complete data image from a backup store, application-specific metadata used to interpret stored data in the context of its original application may be lost in the process.
In view of the above, an effective system and method for allowing an application to perform a variety of operations on backup data stored in a backup store that accounts for these issues is desired.